In lenticular-type three dimensional (3D) photography, the basic process involves taking a plurality of two-dimensional (2D) views from a number of horizontally-spaced vantage points, and compressing these 2D views onto each of the lenticules of a lenticular screen to form a 3D composite image of the scene. The lenticular screen is a sheet of transparent material with the front side embossed with an array of cylindrical lenses, and with the back side coated with a photosensitive emulsion or with the back side attached to a photographic film or paper. If the back side of the lenticular screen is coated with a photosensitive emulsion, usually it is also coated with an additional white coating which serves as a reflective layer and, at the same time, as a protective backing. The 2D views captured by a camera are recorded on a photographic film on a plurality of frames.
The basic process of producing a lenticular 3D photograph from a set of 2D frames has been discussed in detail in a number of books and patent disclosures. For example, L. Dudley in "Applied Optics and Optical Engineering" (R. Kingslake, 1965), discusses a printing method where the lenticular screen is transported intermittently so that each of the 2D images recorded on film is exposed at a different angle. T. Okoshi, in "Three-Dimensional Imaging Techniques" (1978), discusses the use of several projectors to expose a plurality of2D images onto the photographic emulsion. U.S. Pat. No. 4,120,562 (Lo et al.) discloses a scanning method for exposing a number of 2D images at different projection angles. U.S. Pat. No. 4,101,210 (Lo et al.) discloses a method of filling the film area underlying the lenticules by using a plurality of projection lenses. U.S. Pat. No. 5,028,950 (Fritsch) discloses a dual-stage 3D photographic printer in which the examination of the images on film and the projection of images onto the print material are carried out in two separate mechanical stages to allow for the time difference between the two parts of a printing process. U.S. Pat. No. 4,903,069 (Lam) discloses the printing of a machine-readable code on the film at the time of picture taking to indicate the focusing distance.
The basic process in 3D printing involves the projection of a plurality of images in a set of negatives recorded on film, through a projection lens, onto the lenticular print material at different projection angles. In order to accomplish the projections at different angles, a 3D photographic printer must transport at least two of three important elements (the negatives, the projection lens and the print material) to different positions to produce a 3D photograph. By contrast, all of the above-mentioned elements can be stationary throughout a 2D printing process.
In both 2D and 3D printing, the color and density of a negative must be examined, either automatically by an analyzing means or visually by an operator, so that the exposure time and the setting of color filters in the lamphouse can be determined prior to printing.
In 3D printing, because the plurality of images in a set of negatives must be projected onto a single piece of print material to produce a composite 3D photograph, it is required that these images be properly aligned. Thus, it is advantageous to acquire all these images and channel the data to the computer which locates the relative positions of the images for image alignment. In contrast, image alignment is not necessary in 2D printing because only one image is projected onto the print material to produce a 2D photograph.
Presently, one must use a dedicated 2D printer to make 2D prints and use a dedicated 3D printer to make 3D pits. It would be desirable to have a dual-mode printer which can be used to make both 2D and 3D pits, thereby saving time, money, and space. It is to the provision of such a dual-mode printer that the present invention is primarily directed.